U.S. patent application number 13/876940 was filed with the patent office on 2013-10-24 for hybrid drive for a truck mixing drum.
This patent application is currently assigned to SAUER-DANFOSS GmbH & Co. OHG. The applicant listed for this patent is Joachim Hergt, Jan Jakubovic, Peter Krissak, Bert Kroschel. Invention is credited to Joachim Hergt, Jan Jakubovic, Peter Krissak, Bert Kroschel.
Application Number | 20130276577 13/876940 |
Document ID | / |
Family ID | 44741324 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130276577 |
Kind Code |
A1 |
Kroschel; Bert ; et
al. |
October 24, 2013 |
HYBRID DRIVE FOR A TRUCK MIXING DRUM
Abstract
The invention relates to a drive unit for a mixing drum that is
disposed on a motor vehicle, in which an electric motor or a
hydraulic drive comprising a displacement pump and a hydraulic
motor can be used to drive the mixing drum. The low-power electric
motor is used to drive the mixing drum at low rotational speed
during the transport journey of the mixed concrete to the building
site, while the hydraulic drive drives the mixing drum at high
rotational speed during loading, mixing and discharging.
Inventors: |
Kroschel; Bert; (Klein
Ronnau, DE) ; Hergt; Joachim; (Bargteheide, DE)
; Jakubovic; Jan; (Zilina, SK) ; Krissak;
Peter; (Zilina, SK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kroschel; Bert
Hergt; Joachim
Jakubovic; Jan
Krissak; Peter |
Klein Ronnau
Bargteheide
Zilina
Zilina |
|
DE
DE
SK
SK |
|
|
Assignee: |
SAUER-DANFOSS GmbH & Co.
OHG
Neumunster
DE
|
Family ID: |
44741324 |
Appl. No.: |
13/876940 |
Filed: |
October 4, 2011 |
PCT Filed: |
October 4, 2011 |
PCT NO: |
PCT/EP2011/067322 |
371 Date: |
July 12, 2013 |
Current U.S.
Class: |
74/665B |
Current CPC
Class: |
B28C 5/1856 20130101;
Y10T 74/19056 20150115; B28C 5/4213 20130101 |
Class at
Publication: |
74/665.B |
International
Class: |
B28C 5/18 20060101
B28C005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2010 |
DE |
10 2010 047 314.6 |
Claims
1. A drive unit for a mixing drum (8) that is disposed on a motor
vehicle, having a hydraulic drive, which comprises a hydraulic
displacement pump (4) driven by the drive engine (1) of the motor
vehicle and a hydraulic motor (5) fed by said pump, which is
coupled via a truck mixer gearbox (7) to the mixing drum (8) in
order to drive the latter in rotation, having an electric energy
store (2), which is connected to an electrical system (1) of the
motor vehicle, and having an electric motor (6), which can be
activated by the energy store (2) as stipulated by the control unit
(3), that a first clutch (4a) is disposed between the drive engine
(1) of the motor vehicle and the displacement pump (4),
characterized in that a second clutch (5a) is disposed between the
hydraulic motor (5) and the truck mixer gearbox (7), and in that
the electric motor (6) can be connected to the truck mixer gearbox
(7) in such a way that the mixing drum (8) can be driven solely and
directly by the electric motor (6).
2. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, characterized in that a third clutch
(6a) is disposed between the electric motor (6) and the truck mixer
gearbox (7).
3. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, characterized in that in the first,
second and--if present--the third clutch (4a, 5a, 6a) and the
electric motor (6) and the displacement pump (5) are connected to
the control unit (6) and can be actuated via the latter.
4. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, characterized in that the control
unit (3) has control-electronics (3a) and a power stage (3b) for
the drive and the power supply of the electric motor (6).
5. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, characterized in that the clutches
(4a, 5a, 6a) can be actuated electrically or
electromagnetically.
6. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, that there is a rotational speed
sensor (9) for measuring the rotational speed of the mixing drum
(8), which sensor is connected to the control electronics (3a).
7. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 6, characterized in that the rotational
speed sensor (9) is disposed on the truck mixer gearbox (7).
8. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, characterized in that the power
supply of the motor vehicle comprises the electric energy store (2)
or forms the latter.
9. The drive unit for a mixing drum (8) that is disposed on a motor
vehicle as claimed in claim 1, characterized in that the electric
motor (6) and the hydraulic motor (5) for driving the mixing drum
(8) are disposed serially on a drive train (14, 14a).
10. The drive unit for a mixing drum (8) that is disposed on a
motor vehicle as claimed in claim 1, characterized in that the
hydraulic motor (5) can be bypassed by means of a bypass line
(13a), in which a bypass valve (13b) is disposed, in such a way
that the hydraulic motor (5) and the bypass line (13a) together
form the second clutch (5a).
Description
[0001] The invention relates to a drive unit for a mixing drum that
is disposed on a motor vehicle, according to the preamble of claim
1.
[0002] Motor vehicles having equipment for mixing and transporting
concrete to building sites have been known for a long time. They
have a rotatable mixing drum disposed on a motor vehicle chassis
and having a large volume, the rotation of which is usually
effected by a hydraulic motor via a gearbox. The hydraulic motor is
fed by a hydraulic displacement pump, which in turn is coupled to
the drive engine of the motor vehicle and is driven by said pump.
During the transport of the concrete to the building site, the
mixing drum is generally rotated only at about 0.5 to 5 revolutions
per minute, while during mixing and discharging it is operated at
substantially higher rotational speeds, up to 15 rev/min. Concrete
mixing and transporting vehicles of this type are known, for
example from DE 10 2008 017 350 A1 or DE 35 39 550 A1.
[0003] In such concrete mixing and transporting vehicles, also
called a mixer vehicle or truck mixer for short, the problem
results that, when the drive engine of the motor vehicle is at a
standstill, a diesel engine in most cases, the rotation of the
mixing drum necessarily also comes to a standstill. This is
disadvantageous when the drum is filled, since this can lead to
demixing or to premature setting of the concrete, and is therefore
undesired. Therefore, when the mixing drum is filled, in particular
during the transport of the concrete to the building site, the
mixing drum should rotate continuously. This results in the problem
that, when the truck mixer is at a standstill, for example in
traffic jams or during relatively long waiting times until
discharge, the running drive engine of the truck mixer, in most
cases a diesel engine, involuntarily causes exhaust gas and noise
emissions, which are damaging to health, environmentally damaging
and disruptive, in particular in enclosed spaces.
[0004] This problem and solutions thereto are known from the
relevant prior art. For example, in DE 10 2008 017 350 A1, a
dedicated drive independent of the drive engine of the motor
vehicle, a diesel engine, is provided for the hydraulic pump, which
drive is likewise constructed as an internal combustion engine.
[0005] U.S. Pat. No. 3,053,044 shows an additional second hydraulic
high output drive for the rotary drive of a secondary unit. The
high output pump of the hydraulic additional drive can be driven
either via the truck mixer gearbox from the drive engine of the
truck mixer or via an auxiliary drive, which can be an electric
motor. Irrespective of the type of drive of the high output pump,
the mixing drum is set rotating via a hydraulic motor supplied with
pressurized fluid by the high output pump.
[0006] In U.S. Pat. No. 4,542,990, a hydrostatic drive for driving
a mixing drum is shown, wherein the hydrostatic drive, similarly to
U.S. Pat. No. 3,053,044, can be driven on the pump side by an
electric motor. The rotary drive of the mixing drum is also always
hydraulic in U.S. Pat. No. 4,542,990.
[0007] In order to solve the same problem, JP 2003-301802 A
describes a drive unit for a mixing drum that is disposed on a
motor vehicle in which, in addition to the direct drive of the
hydraulic motor via a hydraulic pump coupled to the drive engine of
the motor vehicle, a further hydraulic pump is provided. This
further hydraulic pump can likewise be connected to the hydraulic
motor of the mixing drum via hydraulic lines and valves. The
further hydraulic pump is, however, driven by an electric motor,
which can be fed from the electrical system of the motor vehicle,
that is to say from the usual power supply of the latter. When the
drive engine of the mixer vehicle is at a standstill, the electric
motor comes into action as required and maintains the rotation of
the drum via the hydraulic drive.
[0008] The disadvantage with these solutions is that the separate
drive motor for the displacement pump has to be designed to be so
powerful that it is capable of driving the mixing drum even at the
highest required rotational speed. This applies both to a drive by
an internal combustion engine and to an electric motor. Such a
drive, in which an appropriately dimensioned electric motor is used
to drive a mixing drum directly, i.e. without the interposition of
a hydraulic drive, is described in DE 20 2009 001416 U1.
[0009] A problem that occurs specifically in driving the
displacement pump of a hydraulic drive of the mixing drum by the
drive engine of the mixer vehicle also resides in the fact that the
displacement pump connected to a power take-off of the drive engine
is subjected to all the changes in rotational speed of the drive
engine. As a result of the automated gearbox and the abrupt
accelerations and retardations of the latter, uniform loading of
the hydraulic drive cannot be guaranteed. In addition, the power
take-offs of the drive engine are loaded non-uniformly, which can
disrupt the gear changing operations. In addition, when the
hydraulic drive is operated in the partial load range at about 5
kW, the efficiency is very low.
[0010] It is an object of the invention to provide a drive unit for
a mixing drum that is disposed on a motor vehicle which, as
compared with the prior art, exhibits a further improvement to the
efficiency of the drive system of the mixing drum and of the truck
mixer, the intention being to avoid unnecessary exhaust gas and
noise emissions. The drive engine, in particular the internal
combustion engine of the truck mixer, should be capable of being
shut down while the rotation of the mixing drum is maintained. The
drive system should further be capable of implementation
inexpensively with little effort and robust and reliable in its
execution.
[0011] This object is achieved by the features of the
characterizing part of claim 1, as a result of the fact that a
first clutch is disposed between the drive engine of the motor
vehicle and the displacement pump, that a second clutch is disposed
between the hydraulic motor and the truck mixer gearbox, and that
the electric motor (6) is or can be connected to the truck mixer
gearbox (7) in such a way that the mixing drum (8) can be driven
solely by the electric motor (6).
[0012] According to the invention, in addition to driving the
mixing drum via a hydraulic drive train with displacement pump and
hydraulic motor, an electric motor is provided. This electric
motor, with a relatively low output as compared with the hydraulic
drive, is permanently connected to the truck mixer gearbox
according to one achievement of the object. This means that it is
permanently coupled to the drive shaft of the truck mixer gearbox,
for example by a pair of gear wheels that are permanently
engaged.
[0013] According to a further embodiment of the invention, the
electric motor can optionally be connected to the truck mixer
gearbox, which, according to claim 2, can be achieved by a third
clutch, which is disposed between the output shaft of the electric
motor and the drive shaft of the truck mixer gearbox.
[0014] In both design variants, provision is made for the electric
motor to be used as an alternative drive of the mixing drum only
when the hydraulic drive train is taken out of operation by
disengaging a first and/or a second clutch. The first clutch is
located between the drive engine of the mixer vehicle and the drive
shaft of the hydraulic displacement pump. When this clutch is
disengaged, this pump thus no longer experiences any drive. The
second clutch is disposed between the output shaft of the hydraulic
motor and the drive shaft of the truck mixer gearbox. It is
primarily used to prevent drive power being transmitted to the
hydraulic motor when the mixing drum is driven by the electric
motor. This would lead to the operation of the latter as a pump,
which is already undesired because of the additional loading of the
electric motor effected hereby.
[0015] The electric motor according to the invention is preferably
designed such that its output power is sufficient to drive the
mixing drum in the lower rotational speed range suitable for the
transport of the finally mixed concrete. This rotational speed
range lies between 0.5 and 5 rev/min, which requires a drive output
of about 5 kW. This lies substantially below the output of about
100 kW which is needed to rotate the mixing drum at up to 15
rev/min during loading, mixing and discharging.
[0016] According to the invention, the electric motor is used, for
example, when finally mixed concrete is transported to the building
site. The high-power driving of the mixing drum at high rotational
speed during loading and mixing of the concrete has then already
been completed, and the hydraulic drive train for rotating the
mixing drum is taken out of operation by disengaging the first
and/or second clutch/es as stipulated by the control unit. The
power supply of the electric motor is activated by the control
unit. The electric motor drives the mixing drum via the truck mixer
gearbox, if necessary following engagement of the third clutch.
[0017] After the building site has been reached, the electric motor
can remain in operation until the discharging operation is
required. It is thus possible to bridge over waiting times, in
which the drive engine of the mixer vehicle can also be brought to
a standstill. This avoids unnecessary consumption of fossil fuels
and therefore reduces the exhaust gas environmental pollution. Only
when discharging is to be carried out is the driving of the mixing
drum at high rotational speed required again, for which purpose the
drive engine has to be started up and the hydraulic drive has to be
activated by engaging the first and/or the second clutch.
[0018] In the electronic operating mode, the drive of the mixing
drum is completely isolated from the behavior of the drive engine
and from the fluctuations in rotational speed of the latter during
the transport. Jumps in the rotational speed of the drive engine
are not passed on to the mixing drum. No uncontrolled accelerations
or retardations in the hydraulic drive train for the mixing drum
occur, since the latter is uncoupled from the drive engine.
Load-dependent fluctuations and wear as a result of pressure peaks
in the hydraulic system are avoided. The synchronous running of the
mixer drive and the overall efficiency of the system are better
than in the case of a purely hydraulic drive of the mixing drum in
accordance with the prior art. In addition, the hydraulic drive is
loaded less, since it is not used during the travel to the building
site and, as a result, is spared from sudden accelerations and
pressure peaks.
[0019] The electric motor according to the invention is preferably
fed from the electrical system of the mixer vehicle via a frequency
inverter, which is part of the electric control device of the drive
unit, and the rotational speed of said electric motor is regulated.
The regulation advantageously comprises a rotational speed sensor,
which is preferably disposed on the truck mixer gearbox. The
preferred feeding of the electric motor from the electrical system
means that the power required for the operation of the electric
motor is taken from the on-board battery of the mixer vehicle. This
rechargeable battery, i.e. an accumulator, is fed, for example,
from the alternator of the drive engine of the mixer vehicle. Of
course, a dedicated accumulator, which is independent of the
starter battery of the drive engine of the mixer vehicle, could be
provided for the power supply of the electric motor. This drive
engine is usually an internal combustion engine, preferably a
diesel engine.
[0020] The electric motor for driving the mixing drum can be
connected to the mixing drum gearbox in such a way that, during the
hydraulic driving of the mixing drum, that is to say at increased
rotational speed, in particular during loading, mixing and
discharging, is also driven by the hydraulic drive and thus
functions as a generator in order to supply electrical energy into
the energy store.
[0021] In a further embodiment, the electric motor can also be
incorporated into the drive train in such a way that the electric
motor assists the hydraulic motor during hydraulic driving of the
mixing drum, which means that the rotational speed of the drive
engine of the truck mixer and thus, in the case of an internal
combustion engine, resources can be reduced and the environment is
protected.
[0022] Exemplary embodiments of the invention will be described
below by using FIGS. 1 to 3.
[0023] FIG. 1 shows, by way of example, the main components of a
first embodiment of a drive unit according to the invention in a
schematic illustration.
[0024] FIG. 2 shows, by way of example, the main components of a
second embodiment of a drive unit according to the invention in a
schematic illustration.
[0025] FIG. 3 shows, by way of example, the main components of a
third embodiment of a drive unit according to the invention in a
schematic illustration.
[0026] Illustrated in FIG. 1 is a drive engine 1 which forms the
main drive of the concrete mixing and transporting vehicle, not
shown. This motor vehicle will be called a truck mixer or mixer
vehicle for short below. The drive engine 1 normally used is an
internal combustion engine in the form of a diesel engine. Of
course, the drive engine 1 used for the driving operation of the
motor vehicle can also be a hydraulic motor or hybrid drive which,
however, is normally driven by an internal combustion engine as
main unit. The output shaft 11 of the drive engine 1 is coupled via
a transmission 12 to an electric generator 10, which feeds an
accumulator 17 as power supply 2 of the electrical system of the
truck mixer and keeps it in the charged state. The output shaft 11
can be connected via a preferably electrically, electromechanically
or mechanically driveable and actuable clutch 4a to the drive shaft
11a of a hydraulic displacement pump 4. The delivery output of the
displacement pump 4 can be adjusted in a known way via an adjusting
unit 4b. The displacement pump 4 is connected to the hydraulic
motor 5 by hydraulic lines 13 for the pressurized fluid. The
rotational speed and direction of rotation of said hydraulic motor
5 can be predefined in accordance with the control signals present
on the adjusting unit 4b of the displacement pump 4. The fixed
displacement motor illustrated in FIG. 1 can also be implemented in
another embodiment as a displacement motor with conventional
adjusting mechanism, which is self-evident to those skilled in the
art.
[0027] The output shaft 14 of the hydraulic motor 5 can be coupled
to the drive shaft 14a of the truck mixer gearbox 7 in a
force-fitting and/or form-fitting manner by means of the preferably
electrically, electromechanically or mechanically driveable and
actuable further clutch 5a. The output side of the truck mixer
gearbox 7 is connected to the mixing drum 8 and sets the latter
rotating when a sufficient torque is present on its drive shaft
14a.
[0028] The truck mixer gearbox 7 is conventionally constructed as a
step-down gearbox, for which reason, because of the ruggedness and
the achievable high step-down ratio, epicyclic gearboxes of various
design have become widespread. The drive and output shafts are
normally resiliently mounted and permit the drive shaft 14a to be
pivoted in a limited angular range relative to the mixing drum
8.
[0029] According to the invention, a drive torque acting on the
truck mixer gearbox 7 can alternatively be effected by an electric
motor 6, which is controlled via a control unit 3, which has
control electronics 3a and a power stage 3b. According to the
exemplary embodiment of FIG. 1, for this purpose the electric motor
6 can be connected via a third clutch 6a to the input side of the
truck mixer gearbox 7; the clutch 6a is preferably also designed
such that it can be driven and actuated electrically or
electromechanically. The control signals for this purpose, and also
all the other control signals for the exemplary embodiment shown in
FIG. 1, are generated by the control unit 3 and transmitted to the
individual subassemblies to be controlled via lines 15 illustrated
only by way of example and schematically. It goes without saying
that the control unit 3 is driven automatically as far as possible,
for which purpose sensors or other input means, not shown, are also
present. Manual interventions by the driver of the motor vehicle or
by other operators are also possible, however, for which purpose
switching and operating devices are provided in the driver's cab
and advantageously also on an outer side of the mixer vehicle.
Thus, an operator can choose the operating mode "drive the mixing
drum via hydraulic motor" or "drive the mixing drum via electric
motor" as desired and predefine the respectively desired rotational
speed. It goes without saying that data supplied from the drive
engine via a bus or similar equipment can also flow into the
control of the drive unit.
[0030] Instead of the clutch 6a shown in FIG. 1 between the
electric motor 6 and the truck mixer gearbox 7, according to
another exemplary embodiment of the invention, a direct connection
of the electric motor 6 to the truck mixer gearbox 7 can also be
provided, for example by using the drive shaft 14a. The coupling of
the output shaft 16 of the electric motor 6 to the drive of the
mixing drum is in this case preferably carried out via a pair of
gear wheels, which are in continuous engagement with each other and
of which one is disposed on the output shaft 16 of the electric
motor and another, for example, on the drive shaft 14a of the truck
mixer gearbox 7. The output shaft 16 can, however, also act with
other subassemblies of the truck mixer gearbox, for example the
planet carrier or on the ring gear, in order to ensure the desired
rotation of the mixing drum or to act as generator.
[0031] When the mixing drum 8 is driven by the hydraulic motor 5
with the clutches 4a and 5a engaged, the electric motor 6 in this
embodiment is operated as a generator. The electric power generated
here can advantageously be fed into the electrical system of the
motor vehicle and, for example, in this way assist the charging of
the accumulator of the power supply 2. Of course, the electric
motor 6 in this design of the drive unit can also co-rotate freely
without outputting energy.
[0032] The constructional variant described can also be modified to
the effect that one of the aforementioned gear wheels is provided
with a freewheel, so that the rotation of the drive shaft 14a of
the truck mixer gearbox 7 is not transmitted to the electric motor
6. A freewheel is advantageous when the drive of the mixing drum 8
is designed such that rotation only in one direction is
provided.
[0033] The clutch 6a shown in FIG. 1 between the electric motor 6
and the truck mixer gearbox 7 can be implemented, for example, by
the output shaft 15 of the electric motor 6 and the drive shaft 14a
of the truck mixer gearbox 7 each having a gear wheel which, for
example by means of axial or radial displacement, can be moved
toward each other or away from each other and therefore brought
into or out of engagement with each other. Since the truck mixer
gearbox 7 is substantially disposed in a fixed position on the
motor vehicle, the coupling and uncoupling between the electric
motor 6 and the truck mixer gearbox 7 is carried out, for example,
by the electric motor 6 being displaced. This movement, and also
the actuation of the remaining clutches (4a, 5a, 6a) can be
effected in many ways, for example hydraulically or pneumatically,
but electric, electromechanical or electromagnetic actuation is
preferred. Here, because of their ruggedness in a rough
environment, because of their low wear and the ability to be driven
easily, electromagnets are particularly suitable. However, within
the context of the invention, actuating motors or actuating
cylinders operated by compressed air or hydraulically can also be
used for the actuation of the clutches. In addition, manual
actuation is covered by the idea of the invention.
[0034] The electric motor 6 according to the invention is
preferably connected mechanically to the housing of the truck mixer
gearbox 7, in exactly the same way as the hydraulic motor 5 and the
associated second clutch 5a and the third clutch 6a--if such a one
is present. This housing is advantageously constructed such that
the hydraulic motor 5 and the electric motor 6 can be
flange-mounted on said housing, which makes mounting and
maintenance easier. The couplings 5a and 6a can if desired be
formed integrally with the associated drive, hydraulic motor 5 or
electric motor 6, or with the truck mixer gearbox 7.
[0035] The operating mode of the drive unit of the invention
according to FIG. 1 is as follows: during loading, during mixing
operation or during discharging of the finished mixture on the
building site, the drive of the mixing drum 8 has a high power
demand, which can be in the region of 100 kW. The motor vehicle
which carries the mixing drum 8 is normally stationary here, so
that substantially the entire power of the drive engine 1 is
available. With the first clutch 4a engaged, this power is
transmitted to the hydraulic displacement pump 4 and, in accordance
with the control signals applied to the adjusting unit 4a, effects
a volume flow of pressurized fluid in the hydraulic lines 13. This
flow drives the hydraulic motor 5, which acts on the truck mixer
gearbox 7 via the engaged coupling 5a and thus sets the mixing drum
8 rotating. The truck mixer gearbox reduces the rotational speed in
such a way that the mixing drum 8 executes approximately 15 to 20
revolutions per minute. This relatively high rotational speed is
required for the loading, mixing and discharging of the finished
concrete.
[0036] Since the drive engine 1 of the motor vehicle usually a
diesel engine--which, in this operating mode, runs under relatively
high load in an optimized state--the drive engine 1 operates in a
range that is beneficial with respect to fuel consumption and
reduced pollutant development. At the same time, the charging of
the accumulator of the power supply 2 of the electrical system is
maintained or generated.
[0037] The electric motor 6 provided in accordance with the
invention is preferably not in operation in high-load operation
here, and the third clutch 6a shown in FIG. 1 is disengaged. If
such a clutch is not present, as in the second exemplary embodiment
described, although the rotor of the electric motor co-rotates if
no freewheel is interposed, the electric motor acts here as a
generator. It thus outputs no drive power to the mixing drum but,
if appropriate, charges the accumulator of the power supply 2.
[0038] In driving operation, that is to say during the transport of
concrete, only relatively slow rotation of the mixing drum 8 is
required at only a few revolutions per minute, for which purpose a
drive power of a few kW is adequate. According to the invention,
this power is no longer branched off from the drive engine 2 of the
motor vehicle, as hitherto in accordance with the prior art, but is
supplied directly by the electric motor 6 according to the
invention. For this purpose, the first and/or the second clutch (4a
and 5a) are disengaged, which is done by appropriately driving the
clutches 4a and 5a by the control electronics 3a of the control
unit 3. The displacement pump 4 and the hydraulic motor 5 no longer
experience any drive when the first clutch 4a is disengaged and no
longer act on the mixing drum 8 either. Instead, the electric motor
6 is started and, in the exemplary embodiment according to FIG. 1,
for example, the third clutch 6a is engaged. The torque produced by
the electric motor 6 preferably acts on an input-side drive shaft
14a or 16a of the truck mixer gearbox 7 and, as a result, sets the
mixing drum 8 rotating.
[0039] The power supply of the electric motor 6 is provided via the
power stage 3b of the control unit 3 from the power supply 2 of the
electrical system. This power supply 2 is assisted during driving
operation of the motor vehicle by the generator driven by the drive
engine 1, i.e. the conventional alternator, so that the latter can
also provide the power required for the operation of the electric
motor 6 for a relatively long time.
[0040] In the exemplary embodiment shown in FIG. 2, for example for
the short-term disconnection of the hydraulic drive of the mixing
drum 8, the hydraulic motor 5 which, in this case, preferably
represents a fixed displacement motor, can be bypassed via a bypass
line 13a. To this end, the bypass valve 13b disposed in the bypass
line 13a is opened, as a result of which the hydraulic oil flow
generated by the displacement pump 4 is led past the hydraulic
motor 5. The hydraulic motor 5 thus transmits no torque via the
drive train 14/14a to the mixing drum gearbox 7. This
short-circuiting of the hydraulic motor 5 is equivalent to
disengaging a clutch, since the drive train 14/14a is interrupted.
Consequently, the second clutch 5a in the exemplary embodiment
according to FIG. 2 can be omitted if it is accepted that the
hydraulic motor 5 co-rotates idly when the mixing drum 8 is driven
by the electric motor 6. However, as compared with the mass of the
filled mixing drum 8, the mass of the hydraulic motor 5
additionally to be rotated in this case by the electric motor 6 can
be estimated to be negligibly low.
[0041] In FIG. 2, a gearbox 18 is additionally connected between
the electric motor 6 and the third clutch 6a and can usually be
controlled by means customary in the art in such a way that it is
able to keep the rotational drive speed of the electric motor 6 in
the optimal range, at the same time the rotational speed of the
mixing drum 8 being adjustable. Likewise, and with the same effect,
the gearbox 18 can also be disposed on the drive shaft 16a of the
mixing drum 8. Furthermore, as already indicated previously, a
freewheel for the electric motor 6 can be provided in the gearbox
18, in order that co-rotation of the electric motor 6 is avoided if
the mixing drum 8 is set rotating by the hydraulic drive and no
third clutch 6a is provided in the electromechanical drive train
for the mixing drum.
[0042] In a further exemplary embodiment, which is illustrated in
FIG. 3, the electromechanical drive of the mixing drum 8 via the
electric motor 6 is disposed in series, i.e. serially, with respect
to the hydraulic drive of the mixing drum 8. In the operating
behavior of the two drives, no difference results here from the
parallel dispositions according to FIGS. 1 and 2, but a serial
disposition can be constructed in a more space-saving manner. As
FIG. 3 shows, the output shaft 16 of the electric motor 6 is led
through the hydraulic motor 5 and can drive the mixing drum 8 on
its own and directly. The drive shaft 16a of the mixing drum 8 is
preferably provided with a freewheel as it passes through the
hydraulic motor 5, so that when the mixing drum 8 is driven by the
electric motor 6, the hydraulic motor 5 is not co-rotated. In this
case, the system of the alternative drive possibilities for the
mixing drum 8 of a truck mixer 1 manages with only a single clutch
4a for the mixing drum drive. If the hydraulic drive is shut down
via the clutch 4a, the mixing drum 8 can be set and kept rotating
by the electric motor 6 via the freewheel in the hydraulic motor
5.
[0043] In the exemplary embodiment illustrated in FIG. 3 as well,
the hydraulic motor 5 can be short-circuited via a bypass line 13a
if the bypass valve 13b disposed in the bypass line 13a is opened
and thus the hydraulic fluid supply for the hydraulic motor 5 is
interrupted. The bypass line 13a acts together with the bypass
valve 13b in this case as a hydraulic clutch, so that the
mechanical clutch 5a, as illustrated in FIGS. 1 and 2, for example,
can be omitted. The connection and disconnection of the hydraulic
drive can be controlled here via the bypass valve 13b; the electric
motor 6 can, if appropriate, be taken out of the drive train 14/14a
via a clutch 6a during the hydraulic drive of the mixing drum 8 or,
for example, can also be driven by the hydraulic drive for power
generation and energy recovery. In the simplest case, the clutch 6a
for connecting and disconnecting the electric motor 6 in the drive
of the mixing drum 8 can also be omitted, which means that the
complete auxiliary drive of the truck mixer for rotating the mixing
drum 8 manages with only one clutch 4a.
[0044] Following the model of FIGS. 1 and 2, the possibility is
also provided for the embodiment which is illustrated in FIG. 3 of
separating the electromechanical drive from the drive shaft 16a of
the mixing drum 8 by means of a clutch 6a. A gearbox 18 disposed in
the electromechanical drive for the mixing drum 8 is covered by the
idea of the invention in exactly the same way as a gearbox 18
provided in the serial embodiments of FIGS. 1 and 2.
LIST OF DESIGNATIONS
[0045] 1 Drive engine
[0046] 2 Power supply
[0047] 3 Control unit
[0048] 3a Control electronics
[0049] 3b Power stage
[0050] 4 Hydraulic displacement pump
[0051] 4a First clutch
[0052] 4b Adjusting unit
[0053] 5 Hydraulic motor
[0054] 5a Second clutch
[0055] 6 Electric motor
[0056] 6a Third clutch
[0057] 7 Truck mixer gearbox
[0058] 8 Mixing drum
[0059] 9 Rotational speed sensor
[0060] 10 Generator
[0061] 11 Output shaft of the drive engine
[0062] 11a Drive shaft of the displacement pump
[0063] 12 Transmission
[0064] 13 Hydraulic lines
[0065] 13a Bypass line
[0066] 13b Bypass valve
[0067] 14 Output shaft of the hydraulic motor
[0068] 14a Drive shaft of the truck mixer gearbox
[0069] 15 Electric lines
[0070] 16 Output shaft of the electric motor
[0071] 16a Further drive shaft of the truck mixer gearbox
[0072] 17 Accumulator
[0073] 18 Gearbox
* * * * *